DE-102020112176-B4 - Exhaust aftertreatment methods in a motor vehicle

Abstract

Method for exhaust aftertreatment in a motor vehicle in which an exhaust gas flow (22) coming from an internal combustion engine (12) operating in a high load range is cooled in a braked exhaust gas turbocharger (20) and The cooled exhaust gas flow (28) coming from the exhaust gas turbocharger (22) is subsequently fed to an exhaust gas catalyst (24), wherein the exhaust gas turbocharger (20) is braked by an electric machine coupled to the exhaust gas turbocharger (20) and operated in generator mode characterized by the fact that the electrical energy generated in the generator operation of the electric machine is supplied to an electric traction machine (14) for the electric drive of the motor vehicle.

Inventors

• Thorben Walder
• Frank Schürg

Assignees

• DR. ING. H.C. F. PORSCHE AKTIENGESELLSCHAFT

Dates

Publication Date

20260513

Application Date

20200506

Claims (5)

1. A method for exhaust aftertreatment in a motor vehicle, in which an exhaust gas flow (22) coming from an internal combustion engine (12) operating in a high-load range is cooled in a braked exhaust gas turbocharger (20) and subsequently the cooled exhaust gas flow (28) coming from the exhaust gas turbocharger (22) is fed to an exhaust gas catalyst (24), wherein the exhaust gas turbocharger (20) is braked by an electric machine coupled to the exhaust gas turbocharger (20) and operated in generator mode, characterized in that the electrical energy generated in generator mode of the electric machine is supplied to an electric traction machine (14) for the electric drive of the motor vehicle.
2. Procedure according to Claim 1 , in which the enthalpy of the exhaust gas flow (28) partially used via the electric machine of the exhaust gas turbocharger (22) operated in generator mode is used for the drive power of the motor vehicle.
3. Procedure according to Claim 1 or 2 , in which the total enthalpy of the exhaust gas flow (28) is reduced to such an extent that a heating effect is compensated by an exothermic afterburning of unburned fuel in the exhaust gas catalyst (24).
4. Procedure according to one of the Claims 1 until 3 , in which braking performance and/or throttle position of the exhaust gas turbocharger (20) depends on a mass flow of the The exhaust gas flow coming from the combustion engine (12) is adjusted such that, with an exothermic energy expected in the exhaust gas catalyst (24) at this mass flow of the exhaust gas flow (22), the catalyst temperature of the exhaust gas catalyst (24) is kept below an upper limit temperature provided for the conversion of the exhaust gas flow (22) in the exhaust gas catalyst (24) and, in addition, a required minimum boost pressure of the exhaust gas turbocharger (20) is maintained.
5. Procedure according to one of the Claims 1 until 4 , in which fresh air supplied in the high-load range of the combustion engine (12) and/or the exhaust gas flow (22) leaving the combustion engine (12) operating in the high-load range is cooled by water injection.

Description

The invention relates to a method for exhaust aftertreatment in a motor vehicle, with the help of which combustion gases produced in an internal combustion engine can be cleaned. Out of DE 10 2019 126 611 A1 It is known to couple an exhaust gas turbocharger provided in a drive train of a motor vehicle with an electric machine in order to be able to drive the exhaust gas turbocharger electrically in engine operation and to recuperate electrical energy in generator operation so that the actual turbine power of the exhaust gas turbocharger provides a requested boost pressure as precisely as possible. Out of DE 10 2019 101 508 A1 It is known to operate an electric motor for driving a compressor of an exhaust gas turbocharger also in generator mode for energy recovery into a battery in order to reduce the compressor speed. Out of DE 10 2017 122 895 A1 It is known to use a water injection system to cool compressed fresh air from an exhaust gas turbocharger before combustion in an internal combustion engine in order to reduce the tendency to knock. There is a constant need to ensure good exhaust gas purification in various operating situations of a motor vehicle. The purpose of the invention is to demonstrate measures that enable good exhaust gas purification in various operating situations of a motor vehicle. The problem is solved by a method having the features of claim 1. Preferred embodiments of the invention are specified in the dependent claims and the following description, each of which can individually or in combination represent an aspect of the invention. One embodiment relates to a method for exhaust aftertreatment in a motor vehicle, in which an exhaust gas stream coming from an internal combustion engine operating in a high-load range is cooled in a braked exhaust gas turbocharger and/or by water injection, and subsequently the cooled exhaust gas stream coming from the exhaust gas turbocharger is fed to an exhaust gas catalyst. For exhaust aftertreatment in the catalytic converter, a relatively high operating temperature is generally required to effectively convert the exhaust gases. The operating temperature of the catalytic converter typically ranges between 250°C and 1000°C, particularly between 400°C and 800°C. Such an operating temperature can usually be easily reached and maintained by the temperature of the exhaust gas flow exiting the combustion engine. To prevent the operating temperature of the catalytic converter from dropping too low, especially below its activation temperature, cooling of the exhaust gas flow is generally considered detrimental and should therefore be avoided. However, if the combustion engine is required to deliver particularly high power, it can be operated with a particularly high fuel quantity in the high-load range. This results in a particularly large exhaust gas mass flow with a correspondingly high energy content being emitted from the combustion engine. Furthermore, it can be designed so that in such an operating situation the combustion engine is not operated at a point geared towards particularly low fuel consumption, but rather at a point geared towards high engine power, so that the combustion engine is operated not with a lean fuel/air mixture, but with a stoichiometric or rich fuel/air mixture in the high-load range. This allows for the afterburning of unburned fuel in the combustion engine in an exothermic reaction within the catalyst. The particularly high energy content of the exhaust gas stream and/or the unburned fuel in the exhaust gas stream from a combustion engine operating at high load, especially at full load, could lead to excessive heating of the exhaust catalyst. This could result in operating temperatures within the catalyst that could damage it or impair its service life. However, by cooling the exhaust gas stream—a practice otherwise considered detrimental—in the specific operating conditions of a combustion engine operating at high load, damage to or impairment of the catalyst's service life can be avoided. This ensures effective exhaust gas purification and a long service life in various vehicle operating situations. In one aspect, the exhaust gas flow can be cooled by passing it through the turbine of a decelerated exhaust gas turbocharger. This allows energy to be extracted from the exhaust gas flow to the extent of the braking power applied to the turbocharger. The enthalpy extracted from the exhaust gas flow in the decelerated turbocharger can result in a lower exhaust gas temperature. The exhaust gas flow at the turbocharger outlet is cooled more efficiently than would be possible without deceleration. With a high exhaust gas mass flow rate in a combustion engine operating at high load, cooling the exhaust gas flow in the decelerated turbocharger can achieve a total exhaust gas enthalpy comparable to that of a typical exhaust gas flow in a combustion engine operating at partial load. If necessary, the total enthalpy of the exhaust g